Hydrocarbons, such as crude oil, may be refined to produce various products, such as jet fuel, gasoline, diesel fuel, paraffins, kerosene, naphtha, lubricating oils, asphalts, fuel oil, and liquefied petroleum gases (LPGs) such as propane and butane. Refining generally refers to a group of processes that treat and chemically change hydrocarbons. The refining process for crude oil generally breaks apart the heavier, or more dense, hydrocarbon chains of the crude oil at various pressures and temperatures to produce lighter, or less dense, hydrocarbon fractions. The refining process may result in finished products, such as diesel fuel, and may result in intermediate products, such as fuel oil, that require further processing to produce a finished product. For example, a fuel oil may be refined further through conversion to change its chemical components in a way suitable for use in blending gasoline.
Crude oil may be made up of hundreds of chemical components. Such components may include, for example, alkanes, aromatics, olefins, isomers, and napthenes. Some of those components are heavier than others, and the conversion process may make some components heavier, or may make them lighter, or may change them in some other way to result in certain properties. The conversion process may include, for example, distillation, coking, hydrocracking, fluidized catalytic cracking (FCC), alkylation, de-sulfurization, reforming and isomerization. The conversion process may also rely on catalysts, such as platinum, and other process variables, such as temperature and pressure to effect conversion. Thus, product components may change during the refining process. The refining process may also include blending various intermediate products and additives to create a finished product. Additives may include, for example, ethers and alcohols.
Each product may have various chemical and physical properties that particularly relate to that product's usefulness. Some of those properties may be related to particular components such as benzene. Other properties may be related to the product overall, such as specific gravity. For example, increasing octane may be useful in reducing engine “knocking” when burned, and reducing sulfur may result in lower levels of harmful sulfur dioxide, a combustion by-product.
Petroleum products may be produced to specification. Thus, a refinery in a certain geographic location may develop a product matrix to meet a certain specification based on the types of crude oil that it processes. For example, a retail gasoline station in the northwestern United States may request gasoline blended to have a certain grade, such as regular, or be of a certain type, such as RFG (ReFormulated Gasoline), and be suitable for a certain season, such as winter. A refiner may then develop a product matrix for its location that may characterize the requested grade, type and season. To develop a certain gasoline blend, a refinery may mix various intermediate products, such as those from a vacuum tower, hydrocracker, FCC unit and/or alkylation unit. Different matrices may be provided for other products, and those matrices may vary in complexity. For example, a product matrix for diesel fuel may characterize different components than a gasoline product matrix.
Additionally, petroleum products must comply with the environmental and other regulations of the state in which the product will be sold and used. For example, an environmental regulation may require reduced sulfur in the finished product.
Thus, prior to sending a product to a retailer for sale, a refinery may test or analyze the finished product and/or intermediate products (such as, for example, blendstock for oxygenate blending, or BOB) to determine the properties of the products and to verify those properties against the product specification and regulatory standards. Industry standards, such as ASTM standards, may in some cases define how such tests or analyses are conducted, and often, regulatory agencies will rely on industry standard test procedures to certify a product for sale or use.
Spectrographic analyzers having location- and matrix-specific calibrations may be used by refineries to determine product properties. However, because such calibrations may be location- and matrix-specific, methods using spectrographic analyzers may not comply with the requirements of existing industry standard methods of certifying a fuel product as having specific properties. Regulatory agencies may thus refuse to accept test results based on spectrographic analysis as valid for product certification. In addition, location- and matrix-specific calibrations may make it difficult to compare data between different instruments, sampling or processing techniques, and laboratories, which may, for example, be physically located at the same or different location. For example, a refiner may have multiple refineries in different geographic locations, each processing a different crude oil and using different instruments. Therefore, there is a need for a method and apparatus for standardizing product property values determined by spectrographic analysis.